1. Field of the Invention
The present invention relates to a resonator for operation at several hundred MHz to several GHz used in a portable radio and the like, and particularly, it relates to a dielectric-laminate type resonator.
2. Description of the Prior Art
Conventional resonators are divided roughly into the resonator using a strip line and the resonator using a coil pattern.
As the resonator using the strip line, there is a resonator of 1/2 wavelength whose line is open at opposite ends as shown in FIG. 34 and FIG. 35, and a resonator of 1/4 wavelength whose line is open at one end and short-circuited at the other end as shown in FIG. 36.
Meanwhile, as the resonator using the coil pattern, as shown in FIG. 37, there is the resonator in which a spiral-shaped coil pattern 201 and an earth pattern 203 are formed on both sides of a dielectric layer 202 which is clamped therebetween.
In the above-mentioned conventional resonators, however, such problems as shown hereinafter were encountered respectively.
1. resonator using the strip line
(a) A resonator having the resonance frequency of 2 to 3 GHz becomes substantially large. PA1 (b) In the resonator and the like, it is desirable to adjust the impedance depending on the apparatus into which it is incorporated (to adjust the matching of impedances of the resonator and an apparatus). However, in case of the strip-line type, since the impedance has a specific value for every strip line, it is impossible to adjust the matching even when the input/output position is changed.
That is, lengths L.sub.1, L.sub.2 of the strip line are determined as shown in Equation 1 (resonator of 1/2 wavelength) and Equation 2 (resonator of 1/4 wavelength). ##EQU1## where, .lambda.: wavelength, .epsilon.: dielectric constant of dielectric laminate sheet
Hereupon, at present, a dielectric constant of a dielectric laminate sheet which is capable of being fired simultaneously with silver or copper and has a good temperature characteristic can not be made so large, resulting in about .epsilon.=10. Thus, in the above Equations 1 and 2, when .epsilon.=10, L.sub.1 =15.8 mm and L.sub.2 =7.9 mm, which are very long, thus resulting in a large resonator.
2. resonator using the coil pattern
Since the coil pattern has a spiral shape, magnetic fluxes are influenced by one another between the adjoining patterns, thus an electric current flow is difficult to obtain. Therefore, a substantial resistance increases and the Q value becomes lower.
For example, in FIG. 37, since the electric current flows in the same direction (both in a direction A) in a first pattern piece 201a and a second pattern piece 201b, magnetic fields cancel each other to cause the magnetic fluxes to become coarse, and consequently an electric current flow is disturbed and the substantial resistance is increased.
The resonance frequency of the resonator is decided by the dimension of strip line or coil-pattern, so once the pattern is formed, the resonance frequency can not be adjusted. Therefore, when the dimension of the pattern is in error, the resonance frequency of the resonator is shifted from a predetermined value, resulting in an inferior product.